Flare with safe-and-arm ignition system

ABSTRACT

An aerial flare having a safe-and-arm ignition system in which a radially vable valve element or slider is retained in a safe position obstructing ignition ports by engagement of the slider with interior walls of the flare casing. To deploy the flare, an expulsion charge is electrically detonated, ruptures a frangible barrier, ignites primer in the igniter, and expels igniter-illuminant assembly from the forward end of the casing. When the igniter clears the casing, the slider is powered radially outwardly under the force of a biasing spring to uncover the ignition ports so that the parts are in an arm position. The flaming primer then ignites the illuminant through the open ignition ports.

BACKGROUND OF THE INVENTION

This invention relates to flares having safe-and-arm ignition systems,and more particularly safe-and-arm ignition systems having blocking orinterrupting mechanisms to selectively prevent or permit ignition.

Aerial flares are used for a variety of applications, includingillumination, signaling, marking, decoy, and other purposes. Due to theimportant nature of their uses, such flares require a high degree ofreliability in their ignition systems. The flares must be in a constantstate of readiness, and when the flare ignition system is placed in the"arm" mode, ignition must be certain.

Nevertheless, the flare cannot be carried on a vehicle such as anaircraft in an armed mode at all times. If the flare were to be ignitedbefore it was launched, the vehicle could be damaged or destroyed.Consequently, the flare must be capable of being carried with theignition system in a "safe" mode in which ignition is impossible.Moreover, the ignition system must be compact, lightweight, and capableof switching from the safe to the arm mode quickly and reliably.

Many types of safe-and-arm ignition devices are known in the prior art,each having associated advantages and disadvantages. Some devices aresmall and simple in operation, which allows for reliable operation inthe arm mode. However, the more simple the arming mechanism, the morevulnerable has been the device to accidental ignition. More complexsystems reduce this disadvantage, but only at higher cost andrequirements for more space. None of the prior art ignition systemsprovides the desired combination of high reliability and small size thatwould make them entirely satisfactory in terms of effective andefficient operation.

Accordingly, it is an object of the invention to provide a flare havingan improved safe-and-arm ignition system that overcomes thedisadvantages of the prior art.

Other objects of the invention are to provide a flare having an improvedsafe-and-arm ignition system that positively prohibits ignition whilethe flare illuminant is contained within the flare casing, and thatensures ignition immediately after the illuminant has exited the casing.

Still further objects of the invention are to provide a flare having animproved safe-and-arm ignition system that automatically switches fromthe safe to the arm mode, and accomplishes the foregoing objects withoutsacrificing space desired to be used for illuminant.

Additional objects and advantages of the invention will appear from thefollowing detailed description which, together with the accompanyingdrawings, discloses a preferred embodiment of the invention for purposesof illustration only. For definition of the invention, reference will bemade to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a flare embodyingprinciples of the invention.

FIG. 2 is a longitudinal cross-sectional view showing details of thecasing of the flare of FIG. 1.

FIG. 3A is a longitudinal cross-sectional view showing details of theilluminant of the flare of FIG. 1.

FIG. 3B is an elevational view on line 3B--3B of FIG. 3A, showing theaft end of the illuminant.

FIG. 4A is an elevational view showing the aft end of the igniterhousing of the flare of FIG. 1.

FIG. 4B is a cross-sectional view on line 4B--4B of FIG. 4A.

FIG. 4C is an elevational view showing the forward end of the igniterhousing of FIG. 4A.

FIG. 4D is a cross-sectional view on line 4D--4D of FIG. 4B.

FIG. 5A is an elevational view showing the aft side of the slidercomponent of the igniter of the flare of FIG. 1.

FIG. 5B is a cross-sectional view on line 5B--5B of FIG. 5A.

FIG. 5C is an elevational view of the slider taken on line 5C--5C ofFIG. 5B.

FIG. 6A is a partial longitudinal cross-sectional view of the flare ofFIG. 1, showing the parts of the ignition system in the safe positionshortly after ignition has been initiated, but while the igniter isstill in the flare casing.

FIG. 6B shows the parts of FIG. 6A in the arm position after the igniterhas been expelled from the casing.

FIG. 7A is a cross-sectional view on line 7A--7A of FIG. 6A.

FIG. 7B is a cross-sectional view on line 7B--7B of FIG. 6B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The aerial flare of FIG. 1 comprises a casing 10 containing the internalcomponents of the flare and having a fore-and-aft axis 12. The interiorsurfaces of the casing define a chamber having a relatively larger foreportion 14 (see also FIG. 2) and a relatively smaller aft portion 16,which are sealed from one another by frangible barrier 18. Aft chamberportion 16 contains an expulsion charge 20 which initiates ignition andgenerates an explosive impulse that ruptures barrier 18 and expels thecontents of fore chamber portion 14 through the forward end of thecasing. Expulsion charge 20 is detonated electrically in a conventioalmanner by applying a voltage across electrodes 24A, 24B which protrudefrom the aft end of the charge and are plugged into a suitable,conventional launcher (not shown). As will be discussed in greaterdetail below, activation of the expulsion charge produces flaming gaseswhich ignite a primer carried in the flare igniter 30, after rupturingbarrier 18.

As best shown in FIG. 2, the diameter of fore chamber portion 14 islarger than that of aft chamber portion 16, with a shoulder 28 .beingformed at the juncture of the chamber portions. Barrier 18 at thejuncture of the chamber portions seals fore chamber portion 14 from aftchamber portion 16. Barrier 18 comprises a button 31 that is joined toshoulder 28 by a very thin (e.g. 0.010") connecting annulus 32.Activation of expulsion charge 20 (FIG. 1), which may be of any suitabletype of conventional design, ruptures the barrier at the connectingannulus, and dislodges the button from its position barricading chamberportion 14 from chamber portion 16 (see FIG. 6A).

The flare grain or illuminant 42 is best shown in FIGS. 3A, 3B, and maybe of any suitable, conventional type. The term "illuminant" as usedherein means an emitter of radiation in the electromagnetic spectrum,and may be selected from a variety of conventional, known types on thebasis of the intended use of the flare. Illuminant 42 has an axialrecess 44 in its aft end, in which is embedded a barbed member 94(FIG. 1) by which illuminant 42 is attached to igniter 30. Additionally,the aft end of illuminant 42 includes an annular groove 46 (FIGS. 3A,3B) along which a conventional primer 48 is distributed to foster a moreuniform burn of the illuminant. Igniter 30 (FIG. 1) rests againstshoulder 28 when positioned in fore chamber portion 14. The ignitercomprises a housing 50, detailed in FIGS. 4A-4D, for carrying theremaining components of the igniter. Housing 50 has an aft surface 52that includes a plurality of raised separator elements or lands 54A-54Fwhich engage shoulder 28 (FIG. 1). These raised separators preventincidental contact between the remaining portions of aft surface 52 andbarrier 18 that might rupture connecting annulus 32 and displace button31 prematurely, i. e., before the activation of the expulsion charge.

Two ignition ports or passages 56A, 56B (FIGS. 4A-4D) are formed in thehousing and lead from aft surface 52 to fore surface 58 of the housing.As shown in FIG. 4B, near aft surface 52 each passage includes an areaof enlarged diameter 70A, 70B, for receiving a conventional primercharge 72A, 72B, respectively. These primer charges are ignited byexpulsion charge 20 (see FIGS. 1, 6A) and in turn ignite illluminant 42(see FIG. 6B). The housing also includes a cavity 74 (FIG. 4B) forreceiving the remaining components of the igniter. Cavity 74 may beconsidered as having three regions consisting of a centrally locatedchannel 76 flanked by two slots 78A, 78B (see also FIG. 4D). Theremaining components of the igniter, shown in FIGS. 7A, 7B, are a spring80, a slidably movable valve element or slider 82, and a spacer 84 whichare inserted into the cavity through its open end 92.

Spring 80 is inserted first, so that it engages closed end wall 90 ofchannel 76, as shown in FIGS. 7A, 7B. Next, slider 82 is inserted sothat its front face 104 engages spring 80. As also shown in FIGS. 5A-5C,the slider includes a main body portion 86 with two platelike footmembers 88A, 88B. As shown in FIGS. 7A, 7B, the slider fits into cavity74 with main body portion 86 slidably received in channel 76 and footmembers 88A, 88B slidably received in slots 78A, 78B, respectively (seealso FIGS. 4B, 4D).

As slider 82 is pushed farther into the cavity, its front face 104compresses spring 80. Eventually, the leading edges of the foot membersare contiguous to walls 81, 83 of the cavity as shown in FIG. 7A. Inthis position, feet 88A, 88B block or obstruct passages 56A, 56Brespectively between primer charges 72A, 72B and the fore surface of theigniter housing, which defines the "safe" position (see also FIG. 6A).It is physically impossible for primer charges 72A, 72B to ignite theilluminant while the igniter is in the safe position. When the parts arein the safe position, a hole 106 (FIGS. 5A-5B) formed in slider 82 for aset pin (not shown) is aligned with a similar hole 108 (FIGS. 4A, 4D)formed in the aft surface of the housing. Insertion of a set pin intoholes 106, 108 will retain or lock the slider in the safe positionduring the assembly process until the igniter is loaded into the casing.The final component of the igniter, spacer 84, is positioned in open end92 of the cavity to provide structural strength and support in afore-and-aft direction during the expulsion procedure.

The igniter is attached to the illuminant by assembly boss 94, (FIGS.4B, 4C) which comprises a main body portion 96 protruding forwardly fromthe igniter housing, and a plurality of radially outwardly projectingbarbs 98 embedded in walls 100 of recess 44 (FIG. 3A) as shown in FIGS.1, 6A, 6B. The igniter-illuminant assembly is wrapped in aluminum foil102, as shown in FIGS. 1, 6A-B, 7A-B. The foil prevents the illuminantfrom being ignited by any flaming gases that blow by the periphery ofthe igniter during the expulsion process.

Before the foil-wrapped igniter-illuminant assembly is loaded into thecasing, the set pin is removed from holes 106, 108 in the slider andhousing, respectively. However, care must be taken to manually restrainthe slider in the safe position against the stored energy of thecompressed spring until the igniter is placed in the casing a distancesufficient for the interior walls of the casing to engage and restrainthe slider in the safe position (see FIG. 7A). If the radially outer endportion 77 of the main body of the slider protrudes substantially beyondthe envelope of the igniter housing (see FIG. 7B), it will prevent theigniter from being inserted into the casing. Thus, the flare accordingto the invention can be assembled only when the parts are in the safeposition, which is a further safety feature of the invention.

Once loaded into the casing, the spring biases the main body of theslider radially outwardly so that the outer end 77 of body portion 86 ofthe slider engages the internal surface of the casing, as shown in FIG.7A. This maintains the parts in the safe position as long as the igniteris in the casing. As shown in FIGS. 1 and 2, a breakaway end cap 34 isaffixed to the forward end of casing 10 by a crimp 36 in the casing. Endcap 34 has an O-ring 38 for sealing the chamber against moisture andother contaminants, and a foam pad 40 which fills any void that mayexist between the illuminant and the end cap as a result ofmanufacturing tolerances of the individual components.

Flares made in accordance with the invention, with the igniter in thesafe mode, can be safely transported and affixed to a launcher on thevehicle. In operation, the flare is deployed by applying voltage acrosselectrodes 24A, 24B (FIG. 1) of expulsion charge 20 which ignites,producing flaming gases in an explosive impulse. These gases rupturebarrier 18 at connecting annulus 32 and dislodge button 31 (see alsoFIG. 6A). Once the barrier is ruptured, the flaming gases enter forechamber portion 14, ignite primer charges 72A, 72B, and force thefoil-wrapped igniter-illuminant assembly forward in the chamber todislodge end cap 34. While the igniter slides toward the forward end ofthe casing, the casing is retained on the launcher on the aircraft andthe interior surface of the casing maintains the slider in the safeposition (FIGS. 6A, 7A) thereby preventing the flaming primer chargesfrom igniting the illuminant through passages 56A, 56B that areobstructed by the foot members of the slider.

However, when the igniter is expelled from the fore chamber portion ofthe casing (FIG. 6B), the interior walls of the casing no longer engageand restrain slider 82. When thus freed from restraint, the storedenergy of the spring powers the slider radially outwardly to the armposition (see also FIG. 7B). In moving to the arm position, end portion77 of the slider passes through foil wrap 102 and a slit may bepreformed in the wrap to facilitate this action. In the arm position,the foot members have been displaced to uncover passages 56A, 56B whichare now unobstructed and open for flaming primer charges 72A, 72B toignite the illuminant through the passages and the medium of primercharge 48.

We claim:
 1. An aerial flare, comprisinga casing having a fore-and-aftaxis and having internal surfaces defining a chamber having a foreportion and an aft portion, an igniter disposed in the chamber andslidable in a direction along the fore-and-aft axis of the casing, amass of illuminant disposed in the chamber forward of the igniter andslidable in a direction along the fore-and-aft axis of the casing, meansfor attaching the igniter to the illuminant, expulsion charge means inthe aft portion of the chamber for expelling the igniter and theilluminant from the chamber, the igniter including a housing havingpassage means communicating between the aft portion of the chamber andthe fore portion of the chamber, primer means for igniting theilluminant, the primer means being disposed in the passage means forignition by the expulsion charge means, blocking means mounted on thehousing for movement in a direction transverse to the fore-and-aft axisbetween a safe position in which the blocking means blocks the passagemeans between the primer means and the illuminant, and an arm positionin which the blocking means is displaced from blocking the passage meansand exposes the illuminant for ignition by the primer means through thepassage means, and biasing means operably associated with the housingand the blocking means for biasing the blocking means toward the armposition and into engagement with an internal surface of the casingwhich restrains the blocking means in the safe position while theigniter is within the casing, and breakaway closure means for sealingthe illuminant and igniter in the chamber until broken away by expulsionof the illuminant and igniter by the expulsion charge means.
 2. Theflare of claim 1, in whichthe blocking means is mounted on the housingby guide means defining a cavity in the housing for slidably receivingthe blocking means, and the biasing means powers the blocking means intothe arm position when the blocking means is freed from restraint by theinternal surfaces of the casing upon expulsion of the igniter from thechamber.
 3. The flare of claim 1, in whichthe means for attaching theigniter to the illuminant includes a base portion carried by the housingand a forwardly extending barbed portion embedded in the illuminant. 4.The flare of claim 1, includingsheathing means covering the mass ofilluminant for insulating the illuminant from ignition by blowby aroundthe igniter from the expulsion charge means.
 5. The flare of claim 1,includingfrangible means forming a barrier between the expulsion chargemeans and the primer means until ruptured by activation of the expulsioncharge means.
 6. The flare of claim 1, in whichthe biasing meansincludes a spring.